Opto-electronic modules are modules that transmit and/or receive data optically, for example, using lasers or receivers. An optical connector of some type provides for data passage between the optical devices in the module and other optical components. Typically, such modules also send and/or receive electrical signals, for example, via an electrical connector on a printed circuit board or a backplane. In general, an optical device, which is found in the module, requires several electrical connections. Due to the large number of optical devices that may be present in the module, the number of electrical connections can be numerous. Thus, depending upon the number of optical devices, for space considerations the electrical connector can be configured as a linear or, for a larger of number of optical devices, a two-dimensional array.
In instances where multiple modules are used, they are typically configured in front loading rack-mount systems, which contain racks for receiving modules in much the same way as the frame of a household dresser receives a drawer. Connectors mounted on a backplane at the rear of the drawer or rack mate with connectors mounted on the modules when the modules are seated. Since each rack can contain from a few to hundreds of modules, for ease of maintenance it is important that each module can be serviced (i.e. inserted or removed) independent of as many, preferably every, other module(s) because each unrelated module that must be disrupted in the course of servicing another represents lost capability and, accordingly, potential loss of time and/or revenue. As a result, modules are configured so that they can be inserted and removed through the front panel of the front loading rack-mount system to avoid having to disengage the rack from the backplane and thereby potentially disrupt the operation of one or more unaffected modules.
As the demand for optical communication capability increases, the need for greater numbers of optical devices will similarly increase. However, as noted above, greater numbers of optical devices generally result in larger modules and much larger electrical connectors. Hence, the number of modules that can be fit within a given size front loading rack-mount system decreases. Moreover, since the size of the connector (due to increased numbers of pins or other contact elements) grows faster than the number of devices, the ability to fit more modules within a given size front loading rack-mount system quickly becomes limited by the connector size.
For example, FIG. 1 shows an exemplary opto-electronic module 100 of the prior art. The module 100 has an optical connector 110 on its front side 120 providing access to, in this example, twenty-four optical devices (not shown) such as lasers and/or photoelectors and an electrical connector 130 on its back side 140. The electrical connector 130 is configured to pass through the front panel 170 of the rack (not shown) in order to mate with a complementary connector 150 on a circuit board or a backplane 160 at the rear of the rack. Thus, for ease of maintenance, the connection between the module 100 and the backplane 160 is made by insertion of the module 100 longitudinally through the front panel 170 towards the backplane 160 until the two connectors 130, 150 mate.
FIG. 2 shows the module 100 of FIG. 1 following mating of the two connectors 130, 150 in the above described manner.
FIG. 3 is a rear view of the module 100 of FIG. 1 so that the electrical connector 130 is visible. The electrical connector 130 has an array 180 of pins 190 through which electrical signals can pass between the module 100 and the backplane 160. As noted above, and as is typically the case, the size of the electrical connector on the back side is much larger and contains many more pins than the number of optical devices. Thus, it will be recognized that a mere doubling of the number of optical devices in this example to forty-eight may result in no change in the overall of the module 100 but may require a connector approaching twice the illustrated overall area and thereby far exceed the overall area taken up by the back of the module. As a result, for a given size drawer, the crossover point between increased devices per module versus total number of modules that can be accommodated can shift to a net loss quite quickly.
Thus, there is presently no easy way, for a given size front panel accessible drawer of a rack and a given size and number of modules, to substantially increase the number of optical devices.